Science: Under the weather

THE WEATHER forecast makes prime-time television. It punctuates the morning radio line-up whatever the station. Delicate machines spew out thousands of readings every day from every corner of the country, satellites circumnavigate the world to bring us pictures and there's even a 24-hour cable channel dedicated to the minutiae of passing fronts, troughs and elusive highs.

And what do we do with this deluge of information? We use it to fill gaps in conversations and decide whether to take an umbrella.

But, for centuries, we have also related it - if only in jest and cliche - to our ailments. We talk about being "under the weather", "catching cold" or feeling "sunny", not to mention every family's orthopaedic seer who can forecast impending rain from the twinges in their "bones".

As far back as the third century BC weather was associated with health. The Greek medic Theophrastus said, "If the feet swell, there will be a change to a south wind. This also sometimes indicates a hurricane. So too does it if a man has a shooting pain in his right leg." While modern day medics will appreciate the yearning of John Arbuthnot, royal physician in 1733, to "thoroughly understand the cause of corns aching before the rain from which I would be able to explain the causes of all those pains which affect some bodies in wet weather."

Yet despite this, and a scientific logic that says such an ever-changing mix of temperature, pressure, gases and water must impact in some way on the biological and chemical entities that we are, the influence of the weather on health is largely dismissed as an old wives' tale, too trivial really to have any influence in these days of genetic revelation and magic bullet drugs.

But trawl through medical literature and there is a different story to be found. Tucked away in half-forgotten, often impenetrable medical and meteorological research journals is a body of evidence that links aspects of the weather to a surprising range of health problems.

German medical researchers, for example, suspect that certain wavelengths of electrical activity high in the atmosphere are a trigger mechanism for epileptic attacks. In the US, doctors have discovered patients undergoing tonsillectomy are more likely to haemorrhage if their operation takes place at the beginning of good weather. Another American study found women trying to conceive were more likely to succeed in December and July when the magnetic fields associated with solar winds are low.

In Britain a team of medical weather watchers believe some of the strongest evidence of the health-weather link is to be found in three common conditions: heart attacks, asthma and arthritic pain.

"Heart attacks tend to occur just after a sudden drop in temperature after a long warm spell, or a sudden rise in temperature after a cold spell. When we're not acclimatised, changes in weather put a strain on our body," says Jane Hennessy, who as an MSc student in Applied Meteorology at the University of Reading correlated data from a large study of heart attacks in Oxford with dozens of other studies from around the world. (Findings from studies carried out in locations with climates as different as Montreal and Brisbane show significant peaks in heart attack rates in spring and autumn when sudden changes in temperature are most likely.)

"If the first cold snap doesn't get you then it's likely a later one might unless you protect yourself [ie not rushing out to shovel snow or to start a cold car]," she says, adding that the reason every cold snap doesn't show high levels of heart attack is because the first will have knocked out a large number of susceptible individuals, just like a second hurricane won't blow down as many trees.

According to Dr William Bird, medical supervisor of Jane Hennessy's masters degree and passionate proponent of the health-weather link, there are good medical reasons for this seasonality. Though the body can acclimatise to different weather conditions quite effectively, sudden changes of temperature or humidity place it under extreme stress, and cause it to take emergency precautions to maintain equilibrium, he says. In sudden cold, for example, the peripheral vascular system, which supplies blood to the distant parts of the body, closes down and the blood's stickiness and clotting ability increases by up to 20 per cent to maintain the body's core temperature. This reaction can cause the sudden surge in blood pressure which can trigger off a heart attack in those at risk.

Similarly, sudden heat can also be stressful. The heart is put under pressure as it struggles to cool the body by pumping blood out to the peripheries, and large amounts of energy are consumed in producing sweat.

Some researchers believe that these reactions are conditioned by past - even ancestral - experience of extreme weather and that they can be changed. In Russia, doctors found that the incidence of heart attacks and high blood pressure could be reduced by exposing at-risk people to contrasting temperatures and retraining their body's reaction.

These mechanisms can cause problems for other medical activities too. Take having your tonsils out. That US study which found haemorrhage is more likely if the operation is done at the beginning of a warm spell sounds like mumbo-jumbo. But again it's the body's acclimatisation that provides an explanation, says Dr Bird.

To get accustomed to the warmer weather, the body brings into play its own cooling system. One part of this is to send blood into the airways to be cooled on the in-breath, while heat is expelled on the out-breath. So in warmer weather the tonsil bed becomes engorged with blood and more susceptible to bleeding when cut. On top of this, warmth reduces the clotting factors that will stop a bleed.

"People tend to think that 20th-century life shouldn't be under the influence of the weather. Most of us think we have distanced ourselves from weather, but it can have a tremendous impact," says Dr Bird.

A Fellow of the Royal Meteorological Society, Dr Bird says medical science ignores meteorological affects on the body to its detriment, and believes that looking at weather will lead us to what triggers many diseases in the first place.

The old story of rain-predicting limbs is a classic example, he says. While medics have dithered over what causes the pain in arthritic joints and the NHS spends pounds 300m a year on anti-inflammatory drugs, few have bothered to hear what patients have been telling them for years - that the pain is linked to barometric pressure and humidity.

Beekeeper and gardener Peter Harris suffers from arthritis. He says the weather is a warning sign so accurate that he can plan his week's work by it and pre-empt the worst of the pain by managing his own medication.

"My knees react to the damp, but I feel the change in pressure first in my wrist. When the pressure begins to fall, the ache in my thumb spreads up my arm. When I get the first twinges, I increase the amount of painkillers I'm taking and plan to do less.

"I used to wonder what on earth I could have done to bring this pain on - and of course the tendency is to do less altogether out of fear. But when the penny dropped that it was the weather, I realised I could do much more and not be a couch potato."

As with heart attacks, it's not extreme conditions that cause the problems but the change in temperature and humidity, says Hennessy.

"And the biggest changes in humidity and temperature come before a rain- bearing front. So when people say they can feel it in their bones, they really can - their body is acting like a barometer."

Between 50 and 90 per cent of people with osteo- or rheumatoid arthritis are thought to be sensitive to the low pressure, high humidity conditions typical of approaching rain. And though it's usually dismissed as superstition, Dr Bird says patient experience correlates with at least one hypothesis for the pain in arthritis which suggests that there is hypertension in the capillaries at the end of arthritic bone.

"So if the atmospheric pressure outside drops suddenly, the pressure inside would push the bone out even more, causing pain and possibly inflammation," explains Dr Bird.

But changes in pressure don't just affect the limbs. Fifty one-year-old surgery receptionist Madeleine Joseph says weather- related migraine has ruined many days for her over the years "When the weather gets 'heavy', when a thunderstorm or snow is coming, I feel a terrible pressure building up on my head which grows into a terrific headache. I can often tell what the day is like before I draw my curtains, it's such an ominous, lethargic feeling."

For years she put the headaches down to hormones. "In some ways it's a real relief to know it's the weather and that what I'm experiencing is real. I hated being thought of as a neurotic female!"

Imminent storms are also strongly implicated in breathing problems such as asthma, quite separately from the much talked about problems of air pollution. On 24 June 1994, a tremendous thunderstorm over London flooded accident and emergency departments. Ten times as many people as would normally be seen for breathing problems were registered in the 30 hours after the storm and almost half those affected had never suffered asthma before. Many hospitals ran out of inhalers and drugs, and staff were stretched to the limit.

Similar effects have been linked to thunderstorms around the world and while there are still a myriad of theories about exactly what happens to cause such an epidemic, it's clear weather warnings could help both hospitals and patients to prepare.

Research into the London storm showed no increase in air pollution, but did find a dramatic drop in temperature and an increase in humidity six hours before the influx to casualty departments began. Nine hours before there was also a high grass pollen count - tallying with the theory that the vertical air currents of a storm suck up huge amounts of dust and plant spores, often moving them over large distances before dumping them en masse just before the rain.

On top of this there were over 50 ground strikes of lightning just prior to the deluge - a factor which researchers reckon doubles the chances of an asthma attack. The effect of lightning and charged ions in the atmosphere on health is disputed among meteorological and medical scientists due to a welter of contradictory data. But while some scoff at any link, Drs Baumer and Ruhenstroth-Bauer of the Max Planck Institute in Munich, who are studying the effect of lightning on epilepsy, believe the evidence is gathering weight.

Their studies suggest that the wavelength of lightning can affect the number of fits an epileptic suffers. In the laboratory studies, they have found that chemicals derived from brain connective tissue react to certain wavelengths of lightning. Second, a study of over 3,300 seizures in six patients revealed five had significantly more fits when the lightning was predominantly 28 kilohertz than when it was predominantly 10 kilohertz. Fits were particularly triggered when there was a sudden increase in 28 kilohertz lightning and a corresponding decrease in 10 kilohertz waves, which is what happens with the approach of a cold front.

As well as this, Ruhenstroth-Bauer and Baumer found that road traffic accidents also rise significantly when these changes in electromagnetic conditions occur, suggesting that it could be affecting the behaviour of people who would not consider themselves to be epileptic.

Improvements in medication may mean that many epileptics rarely suffer fits, but a surprise attack can be devastating, not only in terms of confidence, but in practical daily living. Just one fit, for example, brings a driving ban for two years - a disaster which weather knowledge could avert.

It is clear there is more to weather forecasting than meets the eye, but if we want to use it to better our health, we'll need some help, according to Dr Bird. "What we need is a specific medical weather forecast, separate from the general weather forecast, that combines all the factors associated with different conditions.

"What we hope to do is develop computer generated models which will pull together data recorded in previous years. For example, for asthma, we'd pool data on things like temperature, barometric pressure, humidity, pollution, pollen types and from this the model would be able to predict which days will be bad for asthma."

Dr Bird has already run a prototype medical weather forecast in his surgery using "traffic light" signals - green for no problem, yellow for some people might be affected, red for a widespread alert and double red for serious problems - to warn patients with asthma, rheumatoid arthritis and migraine. He also provides a twice weekly forecast to GPs via the computer-distributed World Health Network which gives a risk forecast for asthma, angina, arthritis, sunburn and air quality, and hopes eventually to set up an information system nationwide. Everyone involved - doctors, nurses and patients - could then act in advance, increasing pain killers, avoiding heavy work or driving, doubling up on asthma inhaler doses to prepare for the weatherborn hazard.

"For someone with arthritis this system would enable them to plan their days better. It gives people that bit more information and when people understand what's causing the problem with something like arthritis, they feel more in control and worry less about it."

Actively linking weather to symptoms could also avert the unnecessary anxiety that deterioration in symptoms brings and the upheaval and cost of increasing therapies long term when higher medication might only really be needed for a few days to tide sufferers over the weather conditions.

It could even relieve some pressure on the NHS. Just as farmers use long range weather forecasts to guide their working lives, judging when to harvest, move stock, spray and so on, hospitals and GPs could use it to marshal their resources and provide a better, more efficient service.

For example, outbreaks of flu are often blamed on the weather, but few doctors or health managers would consider looking at the weather forecast for warning of an epidemic. Yet it is common knowledge that it is damp cold that allows flu bugs to flourish and spread - while cold dry weather knocks them dead. Meningitis outbreaks too are associated with sudden increases in humidity.

"Being able to predict a flu epidemic and how long it might go on for would have huge implications for GPs and hospital vaccination programmes. It is easy to trivialise the weather and make it out to be a quaint old wives tale but there is often a good economic case to be made for taking notice," says Dr Bird.

But if such useful forecasting is to become possible in Britain, two key steps are needed, says Dr Bird. First, the country needs a department of environment and health research to bring doctors, atmospheric scientists and weathermen together under one umbrella to gather, test and interpret the evidence. To this end, he is co-operating with Oxford and Oxford Brookes Universities and five general practices in the Anglia region in a bid to get academic funding.

And second, we must start to take our most favoured subject of small talk more seriously.

Last winter eight times more people ended up in casualty with fractures and broken bones in South Thames than usual because of two freezing rain storms, Dr Bird says "But when I phoned the local radio station to warn them what was coming, they just thought I was nutter!" !

ILLUSTRATION BY TOBY MORISON

WEATHER WARNINGS

HOT DRY WINDS

Linked with an increase in mental instability, depression and violence. One explanation is that the winds are loaded with positively charged particles or ions which are thought to affect the production of the mood- elevating brain chemical serotonin. Winds famous for inducing "madness" are the Fohn off the Alps, the Mistral in southern France and the Chinook in Canada. In Britain, warm dry winds blow from the Cotswolds down on Cheltenham, off the Pennines in the north of England and down into the Murray Firth in Scotland.

GREY DAYS

Lack of sunlight affects production of vitamin D which is needed to metabolise the brain chemical melatonin. This can cause depression and lethargy dubbed Seasonal Affective Disorder, but can also improve the chances of conception - minimum melatonin rates correspond to the time of maximum activity in the ovaries.

Lack of vitamin D may raise the risk of developing heart disease as it is involved in cholesterol breakdown.

Some studies have found vitamin D can reduce tumour growth and so by affect breast cancer survival rates.

SUNNY DAYS

May increase the incidence of glaucoma. The constant bright light constricts the pupils and blocks the flow of fluid between the chambers of the eye, increasing the pressure and damaging the retina.

Can cause renal colic due to dehydration. When the kidneys are not thoroughly flushed through, crystals can develop causing fever and pain.

CHANGING TEMPERATURES

Places with big differences in temperature over a 24 hour period appear to have higher levels of schizophrenia than those with more stable temperatures.